Engraved roll application of sealing compounds



1965 D. 'r. ELLIS ETAL. 3,198,111

ENGRAVED ROLL APPLICATION OF SEALING COMPOUNDS Filed April 10, 1961 2Sheets-Sheet 1 STAMPING 1965 D. 1". ELLIS ETAL 3,198,111

ENGRAVED ROLL APPLICATION OF SEALING COMPOUNDS Filed April 10. 1961 2Sheets-Sheet 2 METAL TEMPLATE I COPPER-GLAD ROLL WITH COLD-TOP RESISTFig. 6

United States Patent 3,198,111 ENGRAVED ROLL APPLMATKQN 0F SEALINGCQMPOUNDS Donald T. Ellis, Wellesley Hills, Richard J. Haberlin, Weston,and Robert E. Fogg, Lynn, Mass, assignors to W. R. Grace & (30.,Cambridge, Mass, a corporation of Connecticut Filed Apr. 10, 1961, Ser.No. 102,021 6 (Ilaims. (Cl. 101-170) This invention pertains to a methodand apparatus for applying sealing or gasketing compound in themanufacture of container closures and the like. More particularly, it isdirected to a method of forming can end gaskets on flat stock from whichgasketed can ends can then be fabricated.

Can end gaskets have been formed on punched can ends by nozzle lining.Nozzle lining involves applying a fluid gasket-forming compound througha nozzle to the edge of a can end, usually while spinning the can end ifit is round. This is followed by drying, fiuxing, or curing of thecompound. This method is mechanically complex and is not well suited tothe lining of irregular shaped ends such as rectangular or oval shapes.It has been proposed to form container gaskets by a method akin tosilkscreen printing wherein the gaskets are formed on fiat stock and theclosures with the gaskets are subsequently stamped therefrom. Thetraditional screen printing method, however, is inherently intermittentbecause the metal sheet must be stationary when printed. Theimprovements of the silk-screen method that have been suggested formaking the method continuous are usually mechanically complex and aregenerally unsatisfactory. Also, experimental work has shown that uniformgasket thicknesses and weights are difficult to achieve by this method.

In brief compass, the method of this invention comprises the continuousrotary printing of a fluid or liquid gasket-forming composition of theshape desired on metal sheet followed by conversion of the compositionso printed to form-stable gaskets. The metal sheet is thereafter ,cut orstamped into can ends, crown closures, lug caps and the like in aconventional manner.

The essence of this invention resides in effecting the printing throughthe use of a cylindrical printing surface having the desired design orgasket shape in intaglio. The design is composed of a multiplicity ofsmall inde pendent cavities formed by drilling, engraving, etching orsimilar methods. The configuration of the cavities and the rheologicalproperties of the liquid gasket-forming composition are importantdeterminants to the obtention of (l) proper film thicknesses, (2)adequate transfer of the'fluid composition to the metal sheet, and (3)uniformity in film weights in a single design and between designs, atcommercially acceptable speeds.

Dry film thicknesses in the order of 0.025 to l millimeter are generallyrequired for the types of can-sealing gaskets contemplated and it hasbeen established that the process of this invention is capable ofdepositing films of this thickness in a single step. The presentinvention is particularly suited to the making of gaskets of 0.050 to0.250 millimeter thickness, which thickness encompasses a majority ofthe can-sealing applications. The individual band Widths forconventional can gaskets will usually be in the range of 2 to 8millimeters. The method of this invention is particularly suited to theprinting of gaskets which have two or more bands. It permits placementof dual or multi-band gaskets with a precision that is difiicult toachieve by other methods.

The composition transferred to the metal sheet in the manner of thisinvention is initially in the form of small individual liquid dotswhich, depending on the rheology ice the printing wheel during eachrevolution in any conventional manner, such as by a bath, squeegeeing orspraying. Another important determinant to the successful practicing ofthis invention is the mechanical doctor-ing of excess compound from thebackground of the printing surface. This is done by the use of a rigid,usually metallic, doctoring knife or edge mounted at an angle withrespect to the printing surface which, while scraping away excesscomposition from the background, does not appreciably cause thecomposition to be pulled from or scooped out of the cavities of theintaglio design. The configuration and placement of the cavities alsoaffect the doctoring action. The cavities by and large must beindependent, i.e., not interconnected, to provide a lattice or frameworkwhich supports the doctor blade and they must not be too large becausethe edge of the blade will flex into an overly large cavity and scoopout compound.

Under the proper conditions and with the proper intaglio design, 15 tovolume percent of the material in a cavity will transfer to thereceiving surface, and the cavities after refilling and doctoring butprior to transfer will be to percent filled with the composition. Dryweight variations in any one design, and between designs, are normallyless than $5 percent, and are usually Within :2 percent. This precisionis secured while printing or laying down relatively large amounts ofmaterial, generally over 1 milligram per square centimeter of the band(dry film weight).

While this invention is particularly directed to the manufacture of canend gaskets, it will be appreciated by those skilled in the art that thepresent invention can be usefully applied in any situation where it idesired to place a repeating pattern of a fluid polymer-containingsystem such as a dispersion, solution, melt, or emulsion on a receptiveform-stable substratum. Thus, crown closures can be made by the methodof this invention as well as pregasketed electrical conduit junction boxcovers. Masonite panels decorated with a relatively thick design of anelastomer and useful in the manufacture of glass top tables can also bemade.

The nature and scope of thi invention will become clear from thefollowing discussion and examples made with reference to the drawingsattached to and forming a part of this specification.

In the drawings:

FIGURE 1 schematically illustrates the gasket printing process of thisinvention;

FIGURE 2 shows a portion of the printed metal sheet with the gasketsthereon;

FIGURE 3 is a perspective view of the printing cylinder having a 307 canend design in intaglio;

FIGURE 4 is an enlarged view of a portion of the particular 307 can endintaglio design on the cylinder of FIGURE 3;

FIGURE 5 depicts a much enlarged cross-sectional view of differentshapes the individual cavities making up the intaglio design may have;and

FIGURE 6 schematically illustrates a method of forming an intagliodesign in the printing wheel by etching.

Like parts have the same number in the drawings.

Referring to FIGURE 1, the substratum to receive the elastomergasket-forming compound can be, for example, a sheet 2 of 90 pound tinplate delivered from unwind roll 3. Any weight sheet desired can beused, and dimensionally or form-stable materials other than tin plate,e.g.,

through a bath.8 maintained beneath the roll.

not need to bend' around the roll and can be printed on the underside,while remaining substantially flat.

' The printing speed can be ash-igh as 3 linear meters per second orhigher. Roll 4 can be heated or cooled as re quired by the nature of thecompound. For example, a hollow roll can be used and hot or cold wateror other suitable liquid can be circulated therein, or the roll can beelectrically heated.

,A preferred method of forming the cavities by etching will be describedin greater detail hereafter. Besides acid etching, electrolytic andelectron beam etching can be used as well.

Experimental work has shown that the fraction or percent of compoundtransferred from a cavity is principally a function of the cavity shapeand the rheology of the compound, but is largely unaffected by the sizeof the cavity. A .shallow cavity, to a limit,'transfers a larger 10fraction of its material than a deep cavity. It is to be understood,however, that for two cavities of the same diameter, but materiallydifferent depths, the deeper cavity will transfer the largest totalamount ofcompound because it contains more, although the percentagetransfer will be less than that for the shallow cavity. Stated somewhatdifferently, for a given cavity depth, the quantity of The compound isapplied to the roll by passing the roll Excess compound-is thengrosslyremoved, as the roll rotates, by a rough doctor or squeegeeknife. 9. This is followed by a precision knife-edge doctor blade 10which is used to remove substantially the last traces of compound fromthe background. The under, flat side of the doctor blade 10 is set at anangle of 30 to 60degrees from thetangent at the point of contact. Theblade is preferably oscillated by known mechanical means, e.g., with an.air cylinder. r

The compound on the printed sheet at the point of table roll 7, asillustrated in the drawing,,is still fluid and may or may notbecoalesced. The printed compound is thereafter set'to form-stableshapes. by anyconvenient method, e.g chemical curing, heat drying andcuring, heat fluxing or irradiation; .A-s shown in FIGURE 1, the printedsheet is heat cured in oven 12, and then passed to step 13, when eachgasket is stamped out of the repeated pattern in a conventional mannerto formthe can ends; The perforated scrap is removedat 14, and the canends at 15.

FIGURE 2 illustrates for purposes of clarity the appearance of a sheetafter printing of the compound and heat curing. The metal sheet containsa repeating pattern of a plurality of can end: gaskets 16,-in this case,pear-shaped gasket for 709 x 1011 ham can ends (7% x 10 inches, outsidedimensions, after double seaming). FIGURE 3 shows the printing surfaceof roll 4. A illustrated, it has a plurality of intaglio can end gasketdesigns 17 for a 307 can end (can end size for United States standardNumber 2 can- 3 inches, outside diameter, after double seaming). In somecases, roll 4 may have only one design per revolution.

FIGURE 4 shows a 45-degree arc of one of the 307 can end designs .17 inenlargeddetail. It is composed of a multiplicity of small cavities 18having the desired volume, configuration and spacing. 'While the cavityopenings illustrated are round, they may also be square, triangular,ovoid :and the like. Generally speaking, the depths of the cavities usedin themethod of this invention are considerably greater than thoseencountered in conventional rotogravure printing. The cavities normallyhave a depth over 0.11-20 millimeter, usually over 0.250 millimeter. Itis preferred to use at least two rows of cavities across the width ofthe band.

- FIGURE 5 shows in cross-section three different shapes the individualcavities may have. FIGURE 5a is a shallow dish-shape formed by drillingwith a ball tipped drill or cutter and is the preferred design. FIGURE5b shows. the same. type of cavity but drilled to a greater depth.FIGURE 50 shows the type of cavity which is ,obtained by acid etching.When acid etching is carried out, there is usually some undercutting andthus the cavity bulges in cross-section. When etching is used, it isdesirable in some instances to machine .a few thousandths off thesurfaceof the roll after etching to open up the mouth of the cavity.

material deposited is a linear function of the diameter of the cavity,or approximately so, if the cavity volumes being compared contain thesame percentage of compound, i.e., filling and doctoring has been equal.For a given cavity diameter, the quantity of material tra sferred is asecond order function of the depth and approximates a parabolicfunction.

While the'shape of the cavity, opening isnot too material, it can beseen that the relationship between the surface area encompassed by' thecavity opening to the volume of the cavity is important to the efficienttransferral of c-ompoundfin the heavy film weights desired. There is'alimit on the maximum size and on the spacing of the cavities imposedbythe doctoring step. If the cavity openings are too large, the'doct-orblades will scoop or draw'compound out of the cavities. Cavity spacingis determined by the need to have the printed dots close enoughto permitcoalescencewhile still maintaining a lattice-work, 'i.e., cavityindependence, of sufiicient strength to support the doctor blade withoutdeflection and undue mechanical wear.

In general, it is preferred to use 18 to 75 cavities per squarecentimeter of the intaglio design, and to have the -ratio of the surfacearea encompassed by the opening of a cavity to its volume in the rangeof 5:1 to 50021, prefer- -ably 20:1 to 80:1 centimeters- (volumemeasured without considering undercutting). The distance between theedges of the cavities 'is preferably not furtherthan 0.250 millimeterapart in any direction in order to obt-ain'coalescence, and thelattice-work between the cavities should not be less than 0.025millimeter thick at any point. *Itis also preferred that the areaencompassed by the cavity openings be in the range of 40 to 80 percentof the tot-a1 area included in the inta gli o design.

It has been found that a shallow disc-shaped design as illustrated inFIGURE So as opposed, for example,

to a square or a truncated spher-oid design in cross-section is mosteflicient and .ispreferred. The depth to radius ratio of the disc-shapedcavity is preferably in the range of 1:3 to 1: 8. The radius of thecavity is preferably les than 1 millimeter.

As noted before, the rheology of the fluid ga=sket-forming compound issignificant. While its useful properties may vary somewhat with theprinting speed, film thickness desired,*doctor blade angle, temperature,and the like, certain of the'attributes thatthe compound must have for.successfultransfer can be generally described. The compound must fillthe cavities without too much ,of a meniscus and at a rate consistentwith the speed being .used. Generally, this means that the compound hasa relatively low viscosity as compared to compounds used innozzle-lining operations. ltvmust adequately wet the surface of thesheet being printed to permit transfer. The :internal cohesiveness'mustb'e suflicient to permit cavitation 1 and transfer of a reasonablevolume percent 1 See Eirich, Rheology, volume III, pages to 187, Aea-rdeulie'Press, New York (1960).

, a useful guide.

't'aken'from the Instron recorder.

from the cavity to the surface of the sheet. Its solids content, i.e.,the ratio of dry film weight to wet film weight, must be relatively highin order to secure ade quate film weights with a single printing, and inthe case of heterogeneous polymer systems, to avoid syneritic squeeze,i.e., compressive removal of liquid phase. The solids content of thecompounds used is greater than 40, preferably greater than 70 weightpercent.

The viscosity-shear characteristic of the compound is perhaps its mostimportant property. The compound can range from a slightly dilatantthrough a Newtonian to a pseudo-plastic liquid. This can be moreprecisely expressed by saying that its PIRV slope is within the range of0.70 to 1.05. The Precision Interchemical Rotary viscometer measures theshear stress of a compound over a range of shear rates. The PIRV slopeis the logarithmic rate of change of the shear stress with the shearrate as determined by plotting on log-log paper the shear stress indynes per square centimeter against the shear rate in reciprocalseconds.

The viscoelastic flow property of the compound is also A visooelasticflow valve can be obtained by inserting the tip of a 1.016 millimeterdi- 0 nesium printing wheel.

tained with forces above about 1050 grams per square centimeter.

EXAMPLE I d 72 degree arc of a 307 can end. The band width was 4millimeters. With the smallest cutters, the circular spacing betweenholes was 2 degrees and 3 rows were used for a total of 107 holes perarc, and the arc spacing was uniformly increased up to 4 degrees for thelargest cutter with 2 rows being used for a total of 37 holes per arc.

Three different compounds Were evaluated during this series of tests.

Table 1 Compound A B C Type Polyvinyl-chloride Neoprene in aromatic Lowmolecular weight plastisol. solvent with small peptized neoprene.

amount of filler. Flow properties Cohesive, pseudo- Pseudo-plastic(inter- Mildly cohesive, pseudoplastic. mediate cohesiveness). plastic.Viscoelastic flow, millimeters 14.2 16.0. .5. PIRV slope 0.86 0.85 0.78.Solids content, weight percent 100 82 100. Brooklleld viscosity (LVF5X):

Spindle number 5. Temperature 28 C. 6 r.p.m., centipoises 66,000. 60r.p.m., centipoises 35,500.

1 See United States Patent 2,456,972.

.ameter wire (American S & W music wire, 18 gage) into a drop of thecompound and withdrawing it at about centimeters per minute using anInstron tester. While various Withdrawal rates can be used, the resultsobtained at 50 centimeters per minute are particularly significant.During the withdrawal of the wire from the sample, the viscoelasticelongation (stringing) is recorded with a movie camera and thecorresponding strain is Correlations of the measured viscoelastic flowand the observed strain with the ability of a compound to print indicatethat values in excess of 12 millimeters at 200 milligrams strain aremost satisfactory.

The compound should wet the surface of the plate being printed, i.e., a3 to 6 millimeter diameter drop of compound on the surface should haveno tendency for withdrawal. A slight enlargement of the drop ispreferred. The wetting of the receptive surface can be improved bysuitable means such as coating it with a thin adhesive or lacquer. TheBrookfield viscosity (model LVFSX, No. 4 spindle, 60 rpm, 27 C.) is inthe range of 1,500 to 250,000 centipoises, preferably 1,500

to 60,000 centipoises. Internal cohesiveness as measured by doctoring a0.025 millimeter film of the compound on a 6.45 square centimeter amoothsurface of a metal block, wetted as defined above by the compound,compressing it between a like surface and then pulling the surfacesapart at a rate of 50 millimeters per minute i should give initialforces in the range of 420 to 2100 Cavitation will be obgrams per squarecentimeter.

Precision Iuterchemical Rotary Viscomctcr, see:

cision Scientific Company Instruction Manual, cat. #64945,

After adjusting the machine to obtain uniform transfers, 15.2centimeters Wide strips of pound tin plate were printed on theirunderside at a speed of 25.4 centimeters per second. The wheel rotatedthrough a bath of the compound being tested, and excess compound wa-sdoctored from the wheel prior to the Wheel contacting the trip at thetop of its revolution. The strip almost linearly contacted the wheelunder the impression roll with very little bending.

An average of 10 weighings were made on each of the 16 designs to obtainthe average volume of compound transferred per pass. Percentagetransfers ranged from 22 to 60 percent, based on the amount of compounda design should contain when full as determined from calculations of thecavity volumes. The majority of the data fell in the range of 30 to 45percent transfer. Reproducibilities for any one design and compound,i.e., deviation of any one run from average (in milligrams), were within12.0 percent, except for one run which was $5 percent. The datapredominately fell in the range of -1 percent. The Wet film weightsvaried from 6.7 to 38.8 milligrams per 72 degree arc, with the majorityfalling in the range of 15 to 30 milligrams.

EXAMPLE II Properties of compound-These experiments were carried out ona motor driven bench model printer equipped with an adjustableknife-edged doctor blade and a 20.3 centimeter outside diameter wraparound zinc plate designed to print the proper film volume (0.050 to0.070 cubic centimeter, dry basis) for a 307 can end. The internaldiameters of the bands were 87 millimeters and the outside diameterswere 96 millimeters. Four can persion in water modified with a primarilyzinc oxide 7 7 ends designs in intaglio were placed on the plate using aball or spherical cutter. Table II gives additional de- I tails:

Table II Circle number 1 V 2 3 4 Cutter diameter, millimcters 1. 59 1.59 l 1.98 3.18 Depth, millimeters 0.305 0. 381 0. 381 0. 381' DotSpacing, degrees (alt 2 2 2. 5 3 Number of rows 4 3. 3 2 Total number ofholes- 720 540 432 240, g

1 Between centers of dots in alternate rows.

Compound was placed on the roll by a bath maintained beneath the roll.Excess compound was doctored 01f using two blade angles, 30 degrees and60 degrees from the tangent. Operating speeds were 10.7 and 15.2 linearmeters per minute. 90 pound tin plate strips 15.2 centimeters wide wereprinted with the compound by being contacted with the upper portion ofthe printing roll using a pressure roll to force it down against theprinting roll. Ten weighings were made on each ring printed at eachangle and for each compound. 1

Several different types of compounds were evaluated. Table HI lists thephysical properties of fiveof these compounds by way of example. Thevariety of compound types used establish that the compound system orchemical constituents can vary widely, it only being im-' portant thatthe compounds have the proper rheological properties for printing.

1 doctor blade angle.

experiments established that extremely plasticjmaterials or extremelydilatant materials will not print satisfactor ily. The ideal rheologicaloperating range is slightly on either side of Newtonian, .i.e.,,slightly dilatant, Newtonian or pseudo-plastic. It is difiicult to printa com-, pound whose PIRV slope is' outside the range of 0.70 to 1.05. Atlower values, the extreme plasticity of. the compound prevents fillingofv the cavities and coalescence. The dilatancy of a compound havingahigher value pre vents clean doctoring of the background and also causespoor percentage transfers. V,

At constant speed and with the proper cavity configuration and compoundrheology, the quantity of material transferred from the intaglio designto the metal sheet can be made to be as high as 80 percent by decreasingthe It appears to be desirable in some instances to'design or pitch thedoctor blade such that a hydraulic pressure is created under (andinadvance of) the blade which causes a small amount of compound 'to flowback within the cavity underneath the blade, to the extent perhaps ofcreating a slight minuscus or overfilling of the cavity withsome'compounds. In this connection 1 some benefit can be obtained bypitching the cavities with respect to the tangent, i.e., while thecavities in the roll of this example were drilled perpendicularly to thetangent,

Table III Compound; D H E F G H Type-.. Modified G-RS Rubber latcx..Thermosctting poly- Low molecular Polyvinyl a "in solution. J vinylchloride plasweight neoprene. chloride I i r I V tisol. plastisol. PIRVsloge 0.77 0.82- 0.83-.- 0.87-.- 1.02. Total 5011 s, percen 100. 100100. Brookfield vis., centipoises (LVF5X):

Spindle No 3. Temperature, C 43.5.

r.p.rn 3,500. 1,500.

Compound D was a butadiene-styrene-acrylonitrile terpolymer dispersioncarried in a paraffinic solvent. A large amount of clay filler was usedin this compound.

Compound E was a butadiene-styrene copolymer dis- 0 filler and arelatively large amount of ester gum resins.

Compound F was a dispersion of polyvinyl chloride and an imidazolinecrosslinking agent modifiedwith a moderate amount of a primaryplasticizer blend. 7

Compound G was a highly mechanically and chemically peptized neopreneformulation modified, principally with inorganic fillers and mixedhydrocarbon plasticizers.

Compound H consisted of 55 weight percent of a dispersion gradepolyvinyl chloride resin admixed with percent ofdi-Z-ethylhexylphthalate, 6.5 percent titanium dioxide, 0.25 percentactivated carbon black, and 2.5 percent of. a refined paraffin wax. Thecomposition was prepared by first melting the wax in about /3 of theplasticizer at 66 C. and then blending the remaining in gredients in atabout 50 C., followed by immediate cooling. ,This compound had aspecific gravity of 1.27. It was developedspecifically for use on vinyllacquered tinplate. A 2.5 millimeter thick ,filrn of this compound canbe fused in one minute at 195 C. Compounds D through H printedsuccessfully although" there wereyariations in the'film weights as aresult of compound characteristics, and changes in speed and doctorblade angle. Compound E had the tendency to dry out and form deposits inthe cavities. This can be ovefcome by proper humidification oftheatmosphere. Ring drilled 0 to degrees from the per- Table IV V RESULTSWITH COMPOUND D [75'weight percent total solids-15.2 meters per minute]Circle number 1 2 I 3 4 Theoretical dry weight containcd in cavities,milligrams. 127 r 142 146 137 Percent transfer: V

30 blade angle 66 82. 5 43 79. 5

60 blade angle 71 26 43. 5

, 1 Not accurate-cavities improperly drilled,'consistency between runsis significant.

Table V more clearly. shows the elfect of doctor blade angle on thepercentage transfer of compound.

9 Table V PERCENT TRANSFER VS. BLADE ANGLE [15.2 meters per minute]Percent Transfer Compound 30 angle 60 angle EXAMPLE III plicity ofminute independent recessed cavities with the surrounding continuouslattice-work being formed from the original surface of the wheel, i.e.,the lattice-work of the design is on level with the urrounding surfaceor background of the wheel, and serves to support the doctor blade. Inthe preferred embodiment, directed to the manufacture of can ends, thecavities have substantially identical dimensions and there is nointentional variation either in the spacing of the cavities within thedesign or in the depth, volume or width of opening of the cavities. Thishelps to assure that uniform film weights will be secured. In otherapplications, of course, it may be desirable to have some gradation.

The etching preparation procedure can also be used to prepare thin flator curved perforated plates useful in compound printing processessimilar to silk-screen printing. In this arrangement, the holes gothrough the metal sheet, and compound is forced through the holes fromthe reverse side by a squeegee on to the plate being printed.

Having described this invention, what is sought to be protected byLetters Patent is succinctly set forth in the following claims:

What is claimed is:

1. A method of printing a repeating pattern of a liquid polymericcomposition on a form stable sheet comprising Table IV Circle number 1-M2-M 3-M 4-M 3-E 4-E Cutter diameter, millimeters 1.10 1. 59 1. 98 1. 98Dot diameter millimeters (e 1.03 1.27 1. 52 1.58 1 1 58 Dot depth,millimeters 0. 381-0. 405 0. 355-0. 381 0. 381-0. 405 0. 381-0. 405 0381-0. 405 0 381-0. 405 Dot spacing, degrees (alt 2 2. 5 2. 5 2. 5 2. 5Number of rows 4 3 3 4 3 4 Total number of holes I" 720 540 432 576 432576 Circle diameter, millimeters:

Internal 87 87 87 83 87 83 Outside 96 96 96 96 97 96 With reference toFIGURE 6, brass templates 20 were prepared with the cavities of thedesign drilled approximately 0.381 millimeter undersize. This reductionin cavity diameter allows for the horizontal etching that occurs duringthe vertical etching, which is extensive as compared to the mild etchingused to prepare rotogravure plates. Any form-stable material such as aplastic or aluminum can be used as the blank from which the template isprepared.

Each brass template was used as a photographic negative to produce apositive film by photographing the template image through a fine mesh(150 line) screen 21, using a Cronar type of film 22, which isdimensionally stable. The screen was superimposed on the template toreduce undercutting during the etching. The use of the screen resultedin the photographic positive 22 of the template dots being composed of aregular pattern of very minute dots. The positive was developed in aconventional manner.

The copper clad roll 24 was treated with a photosensitive resist, KodakPhoto Resist (Eastman-Kodak Company, catalog C., 1959), and the image ofthe positive was transferred thereto using carbon arc light through thepositive. When developed in a conventional manner, the black areas ofthe positive, i.e., the screen grid or framework, became the whiteetchable areas on the roll. The images were then incrementally etched ina conventional manner using an iron perchlorate solution and until thedesired depths were reached. The iron perchlorate solution was sprayedonto the roll while rotating the roll. The solution was collected indrip pan 25 and recycled by pump 26 and spray nozzle 27.

It can be seen that with both the machining and etching methods ofpreparing the printing wheel, the intaglio design in the surface of thewheel is composed of a multi- (1) passing said sheet under an impressionroll and uniformly and evenly placing a surface thereof in contact witha portion of a rotatable cylindrical printing surface having an intagliodesign of the desired configuration,

(a) said intaglio design comprising a multiplicity of minute independentcavities ranging from 18 to 75 per square centimeter,

(1) said cavities having a depth of at least 0.120 millimeter and (2) anenclosed surface area to volume ratio in the range of 5:1 to 500:1centimeterv (a) said enclosed surface composing 40 to of the surfacearea encompassed by said design,

(2) filling said cavities with a liquid gasket-forming polymericcomposition (21) having a PIRV slope in the range of 0.70 to (b) aviscoelastic flow value greater than 12 millimeters,

(c) a solids content greater than 40 weight percent and (d) is capableof wetting the surface of said sheet,

(3) removing excess composition from the background of said design, andthen (4) transferring a portion of the composition in said cavities tothe surface of said sheet,

all while rotating said printing surface to produce a repeating patternof said design.

2. A method according to claim 1 wherein said cavities are disc-shapedwith a ratio of the depth to the radius of the open end thereof being inthe range of 1:3 to 1:8, said radius being less than one millimeter.

3. A method according to claim 1 wherein said design is a can end andthe pattern is thereafter set to coalesced form-stable, the dry weightvariation between the designs of said pattern being less than i% r 1 4.A method of printing a sheet metal blank witha plurality of uniformlyspaced elastomeric shapes having a dried film thickness infthe range of0.050 to 0.250 milli meter, a dry film weight greater than 1 milligramper square centimeter and suited for stamping into gasketed closurescomprising V (1) passing arsheet metal blank under an impression rolland uniformly and evenly placing the under surface thereof in contactwith a portion of a rotating cylindrical printing surface having aplurality of intaglio designs therein of the desired configuration, (a)each of said designs being filled with a liquid gasket-forming polymericcomposition (1) having a PIRV slope in the range of 0.70 to 1.05, p (2)a viscoelastic flow value greater than 12 millimeters,

(3) a solids content greater than 40 weight weight percent and I (4) iscapable of wetting the surface of said 1 metal blank, (b) each of saidintaglio designs comprising a multiplicity of-independent minutecavities (1) having a depth of at least 0.120 millimeter and (2) anenclosed surface area to volume ratio;

in the range of 5:1 to 500:1 centimeters- (a) said enclosed surfacecomposing 40 to 80% of the surface area encom passed by said design,

(2) transferring liquid composition from said cavitie to the surface ofsaid metal blank, (3) continuing rotation of said printing surface,

(4) refilling said cavities with said liquid compositon,

(5) removng excess composition from the background of said printingsurface and repeating the printing repeating pattern of can end gasketshaving dried film weights greater than 1 milligram per square centimeterand a band width in the range of 2 to 8 millimeters are formed on ametal sheet and gasket can ends are subse- 12 quently formed therefrom,an improved method of forming said repeating pattern comprising thesteps of (1) printing said metal sheets with said repeating pattern bycontacting said sheet with a rotating cylinder having saidpattern'incised therein in intaglio,

(a') the intaglio pattern being composed of a multiplicity ofindependent cavities (1) having a depth greater than 0.120 millimeterand (2) an enclosed surface area to volume ratio in the range of 5:1 to500:1 centimeters- (a) said enclosed surface' composing 40 to of thesurface area encompassed by said design, (3) there being in the range of18 to 75 of said cavities per square centimeter of said band, (4) saidcavities at the time of contact with saidmetal sheet being in the rangeof 'to filled with g (b) a liquid gasket-forming polymeric compositionhaving V I I (1) a PIRV slope in the range of 0.70 to 1.05, (2) aviscoelastic flow value greater than 12 millimeters, p

(3) a solids content greater than 40 weight {percent and (4) is capableof wetting the surface of said 7 metal sheet, 1 (2) transferring in therange of to 50% of said composition to said metal sheet on contact, 3)continuing rotation of said cylinder, (4) refilling said cavities withsaid composition, (5 removing excess composition from the background ofsaid pattern by doctoling and (6)v repeating the cycle.

References Cited by theExaminer U TED STATES T N S 854,676 5/07 Spitzer101-401 1,273,993 7/18 Blecher 101-401, 1,878,895 9/32 Schutte 101 -1292,147,651 2/39 Jones et a1. 101-170 2,183,222 12/39 J Luehrs 101-532,292,569 8/42 King 101-170 2,370,461 2/45 Heberlein et a1. 96372,486,258 10/49 Chavannes 101-426 2,811,444 10/57 Wattier 96-373,029,765 4/62 Navikas; r 3,036,927 5/62, Ier o'the.

ILLIAM B. PENN, Primary Examiner.

ROBERT A. LEIGHEY, DAVID KLEIN, Examiners.

1. A METHOD OF PRINTING A REPEATING PATTERN OF A LIQUID POLYMERICCOMPOSITION ON A FORM STABLE SHEET COMPRISING (1) PASSING SAID SHEETUNDER AN IMPRESSION ROLL AND UNIFORMLY AND EVENLY PLACING A SURFACETHEREOF IN CONTACT WITH A PORTION OF A ROTATABLE CYLINDRICAL PRINTINGSURFACE HAVING AN INTAGLIO DESIGN OF THE DESIRED CONFIGURATION, (A) SAIDINTAGLIO DESIGN COMPRISING A MULTIPLICITY OF MINUTE INDEPENDENT CAVITIESRANGING FROM 18 TO 75 PERCENT SQUARE CENTIMETER, (1) SAID CAVITIESHAVING A DEPTH OF AT LEAST 0.120 MILLIMETER AND (2) AN ENCLOSED SURFACEAREA TO VOLUME RATIO IN THE RANGE OF 5:1 TO 500:1 CENTIMETERS-1, (A)SAID ENCLOSED SURFACE COMPOSING 40 TO 80% OF THE SURFACE AREAENCOMPASSED BY SAID DESIGN, (2) FILLING SAID CAVITIES WITH A LIQUIDGASKET-FORMING POLYMERIC COMPOSITION (A) HAVING A PIRV SLOPE IN THERANGE OF 0.70 TO 1.05, (B) A VISCOELASTIC FLOW VALUE GREATER THAN 12MILLIMETERS, (C) A SOLIDS CONTENT GREATER THAN 40 WEIGHT PERCENT AND (D)IS CAPABLE OF WETTING THE SURFACE OF SAID SHEET, (3) REMOVING EXCESSCOMPOSITION FROM THE BACKGROUND OF SAID DESIGN, AND THEN (4)TRANSFERRING A PORTION OF THE COMPOSITION IN SAID CAVITIES TO THESURFACE OF SAID SHEET, ALL WHILE ROTATING SAID PRINTING SURFACE TOPRODUCE A REPEATING PATTERN OF SAID DESIGN.